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During pregnancy the plasma volume increases by 40-50% and the red blood cell volume increases only by 20–30%. [22] These changes occur mostly in the second trimester and prior to 32 weeks gestation. [24] Due to dilution, the net result is a decrease in hematocrit or hemoglobin, which are measures of red blood cell concentration.
Alcohol: Use during pregnancy can cause fetal alcohol syndrome and fetal alcohol spectrum disorder. [67] Tobacco use: During pregnancy, causes twice the risk of premature rupture of membranes, placental abruption and placenta previa. [68] Also, it increases the odds of the baby being born prematurely by 30%. [69]
Hemoglobin has an oxygen-binding capacity of 1.34 mL of O 2 per gram, [6] which increases the total blood oxygen capacity seventy-fold compared to dissolved oxygen in blood plasma alone. [7] The mammalian hemoglobin molecule can bind and transport up to four oxygen molecules. [8] Hemoglobin also transports other gases.
The cells in the human body are not outnumbered 10 to 1 by microorganisms. The 10 to 1 ratio was an estimate made in 1972; current estimates put the ratio at either 3 to 1 or 1.3 to 1. [300] The total length of capillaries in the human body is not 100,000 km.
The Mentzer index, described in 1973 by William C. Mentzer, [1] is the MCV divided by the RBC count. It is said to be helpful in differentiating iron deficiency anemia from beta thalassemia trait. [2] [3] The index is calculated from the results of a complete blood count.
Typically, the cells of female humans contain two X chromosomes, while the cells of male humans have an X and a Y chromosome. [22] During early fetal development, all embryos have phenotypically female genitalia up until week 6 or 7, when a male embryo's gonads differentiate into testes due to the action of the SRY gene on the Y chromosome. [23]
The 10 to 1 ratio was an estimate made in 1972; current estimates put the ratio at either 3 to 1 or 1.3 to 1. The total length of capillaries in the human body is not 100,000 km. That figure comes from a 1929 book by August Krogh, who used an unrealistically large model person and an inaccurately high density of capillaries.
The mortality rate of pregnant and recently pregnant women in the United States rose almost 30% between 2019 and 2020. [7] According to the CDC, a study that included data from 36 states found that more than 80% of pregnancy-related deaths were preventable between 2017 and 2019. [8]